The gas diffusion media component of a proton exchange membrane fuel cell, also known as polymer electrolyte membrane fuel cell, is commonly composed of a non-woven carbon fiber paper or a woven carbon cloth. The gas diffusion media component may be treated in order to render the material hydrophobic. Typically, a hydrophobic layer is deposited on one of two faces of the gas diffusion media material. Suitable hydrophobic layers can be formed using hydrophobic polymers such as polyvinylidene fluoride (PVdF), fluoroethylene propylene (FEP), and polytetrafluoroethylene (PTFE). As an alternative to the hydrophobic polymers mentioned, other organic and inorganic hydrophobic materials may also be used. The thickness of the hydrophobic layers is typically 5 to 40 micrometers. In addition, a microporous layer may be applied to the gas diffusion media layer for more effective water management, or to be more specific, to provide a desired mass transport characteristic. Under high current density operations of the fuel cell, the microporous layer must have the ability to move products out of the microporous layer and let reactants reach an underlying catalyst layer.
Recently, carbon corrosion has been identified as part of the voltage degradation that occurs during lifetime operation of polymer electrolyte membrane fuel cells. Carbon corrosion may occur both on the catalyst electrodes and the gas diffusion media layers. The portion of degradation that can be attributed to each component is difficult to separate as they cannot be isolated in situ.
Heretofore, those skilled in the art have used carbon black, graphite, and carbon nanotubes as components in microporous layers. However, each of these materials have different structures, primary particle sizes, primary aggregate sizes, BET surface area, pore size distribution, oil absorption, etc. Further, each of these materials will give different in situ performance when incorporated into a microporous layer. A type of carbon black frequently used in microporous layers is acetylene black, but others commonly used include Vulcan SC-72, Black Pearls 2000, etc.